ResolvinE1对高危角膜移植免疫排斥反应的抑制作用

Experimental study on inhibiting graft rejection following high-risk cornea transplatation by resolvinE1 in mice

背景 以往防治角膜移植术后排斥反应的药物存在诱发局部或全身不良反应的风险，研究表明resolvinE1（RvE1）能够调节辅助性T细胞1（Th1）型免疫反应，但其对高危角膜移植术后的植片排斥反应有无抑制作用尚不清楚。目的观察高危角膜移植动物模型局部应用RvE1对植片免疫排斥反应的抑制作用。方法 以BALB/c小鼠为受体、C57BL/6小鼠为供体行角膜移植术。采用随机数字表法将90只BALB/c小鼠随机分成异体角膜移植组、异体角膜移植＋RvE1组和自体角膜移植组，每组各30只。BALB/c小鼠右眼先用缝线法刺激2周以建立高危角膜移植眼模型，然后行穿透角膜移植术。异体角膜移植组和异体角膜移植＋RvE1组小鼠右眼行异体角膜移植，自体角膜移植组小鼠将右眼角膜植片旋转180°后缝合于植床上。异体角膜移植组及自体角膜移植组小鼠术后每日用生理盐水10 μl结膜下注射1次，异体角膜移植＋RvE1组小鼠术后同法注射终质量浓度为0.1 μg/μl的RvE1 10 μl，连续7 d。术后裂隙灯显微镜下观察小鼠角膜植片反应并对其排斥反应进行评分。术后21 d处死各组小鼠各20只，收集小鼠术眼角膜、眼球和术眼侧颈部淋巴结，采用苏木精－伊红染色法观察各组小鼠角膜植片的组织病理学变化；采用免疫组织化学法检测术眼角膜中CD4及γ干扰素（IFN-γ）的表达；采用流式细胞术检测术眼侧颈部淋巴结淋巴细胞中Th1细胞（CD3＋CD8a－IFN-γ＋）比例；采用荧光定量PCR法检测Th1细胞相关因子白细胞介素-2（IL-2）、肿瘤坏死因子-α（TNF-α）、IFN-γ及T-bet mRNA的相对表达水平。结果 异体角膜移植＋RvE1组小鼠角膜植片存活时间为（28.5±1.7）d，明显长于异体角膜移植组的（14.0±1.6）d，差异有统计学意义（t＝4.14，P〈0.001），自体角膜移植组小鼠植片在术后50 d存活率为100%。苏木精－伊红染色显示，异体角膜移植＋RvE1组和自体角膜移植组小鼠角膜植片水肿及炎性细胞浸润程度均轻于异体角膜移植组。免疫组织化学法检测显示，各组角膜全层均有CD4表达，而IFN-γ主要表达于角膜上皮层，异体角膜移植组小鼠角膜组织中CD4和IFN-γ阳性细胞数均明显多于异体角膜移植＋RvE1组和自体角膜移植组。流式细胞术检测显示，异体角膜移植＋RvE1组和自体角膜移植组小鼠淋巴细胞中Th1细胞比例分别为（1.07±0.25）%和（0.85±0.12）%，明显低于异体角膜移植组的（1.56±0.20）%，差异均有统计学意义（均P〈0.05）。荧光定量PCR检测显示，异体角膜移植组小鼠角膜中IL-2、TNF-α、IFN-γ及T-bet mRNA的相对表达量明显高于异体角膜移植＋RvE1组和自体角膜移植组，差异均有统计学意义（均P〈0.05）。结论 RvE1可抑制小鼠高危角膜移植排斥反应，作用机制可能与其下调角膜植片和淋巴细胞中Th1细胞及相关细胞因子的表达有关。

Background The conventional drugs for preventing and treating graft rejection have the risks of inducing adverse responses.Researches showed that resolvinE1 （RvE1） can regulate Th1 cell-mediated immunoreaction.However, whether RvE1 has an inhibit effect on high-risk corneal graft is unclear now. Objective This study was to investigate the effects of RvE1 on immune rejection in high-risk corneal grafting mouse models.Methods SPF BALB/c mice were used as recipients, C57BL/6 mice were as donors.Ninety BALB/c mice were divided into corneal allograft group, corneal allograft＋ RvE1 group and corneal autograft group according to random number table.High-risk corneal graft models were established by corneal suturing for 14 days and followed by penetrating keratoplasty in recipients.Allograft keratoplasty was performed on the right eyes in the mice of corneal allograft group and corneal allograft＋ RvE1 group, and self-corneal graft rotated 180°was transplanted on the right eyes in the mice of autograft group.Normal saline solution of 10 μl was subconjunctivally injected after surgery once per day for 7 days in the corneal allograft group and corneal autograft group, and 10 μl RvE1 （1 μg） was used in the same way in the corneal allograft＋ RvE1 group.The recipient eyes were examined for potential rejection signals with slit lamp microscope and calculated the mean survival time and rejection index （RI）. The histopathology was examined 21 days after modeling by hemotoxylin and eosin staining.The expressions of CD4 and interferon-γ （IFN-γ） in the corneas were detected by immunohistochemistry.Th1 cell （CD3＋ CD8a-IFN-γ＋ ） percentage in draining lymph nodes were measured by flow cytometry.The mRNA expression levels of interleukin-2 （IL-2）, tumor mecrosis factor-α （TNF-α）, IFN-γ and T-bet were detected by real-time fluorescence quantitative PCR.Results The mean survival time of grafts was （28.5±1.7） days in the corneal allograft group, and that in the corneal allograft＋ RvE1 group was （14.0±1.6） days, showing a significant difference between them （t=4.14, P〈0.001）, while the survival rate was 100% at 50 days after modeling in the corneal autograft group.Corneal edema and inflammatory cell infiltration were slight in the corneal allograft＋ RvE1 group and corneal autograft group compared with corneal allograft group.CD4 was positively expressed in corneal tissue, and IFN-γ was expressed in corneal epithelium.The CD4＋ and IFN-γ＋ cell number was decreased in the corneal allograft＋ RvE1 group and corneal autograft group compared with corneal allograft group under the fluorescence microscope.The percentages of Th1 cells in lymph cells of corneal allograft ＋ RvE1 group and corneal autograft group were （1.07±0.25）%, （0.85±0.12）%, respectively, which were significnatly lower than （1.56±0.20）% in the corneal allograft group （both at P〈0.05）. The expressions of IL-2, TNF-α, IFN-γ and T-bet mRNA in the corneal tissue in the corneal allograft group were higher than those in the corneal allograft＋ RvE1 group and corneal autograft group （all at P〈0.05）.Conclusions RvE1 inhibits graft rejection in high-risk allograft mouse models probably by down-regulating the Th1 cell percentage in lymph cells and the expression of inflammation-related cytokines in corneal grafts.